Abrading – Machine – Rotary tool
Reexamination Certificate
1999-09-10
2002-03-12
Eley, Timothy V. (Department: 3723)
Abrading
Machine
Rotary tool
C451S285000, C451S533000, C451S530000
Reexamination Certificate
active
06354925
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application claims the priority benefit of Taiwan application serial no. 88114312, filed Aug. 21, 1999, the full disclosure of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates in general to a chemical mechanical polisher. More particularly, this invention relates to a composite polishing pad used in a chemical mechanical polisher.
2. Description of the Related Art
Surface planarization is a very important technique that directly affects the precision of a photolithography process. Only when the surface is planarized, a scattering effect of the exposure light can be avoided to transfer a pattern with fidelity.
Currently, two planarization techniques including spin-on-glass (SOG) and chemical mechanical polishing (CMP) have been widely used in industry. As the semiconductor fabrication technique has approached the deep sub-micron regime, the required level of planarity can not be achieved using the technique of spin-on-glass. The only technique to provide the required level of planarity in a very large scale integration (VLSI) or ultra large scale integration (ULSI) is chemical mechanical polishing. In the chemical mechanical polishing process, a polishing theory similar to that used for a grinder is used with the aid of a chemical reagent. The uneven surface profile is thus smoothed. With an appropriate control of the polishing parameters, about 90% of planarity can be achieved using chemical mechanical polishing.
FIG.
1
A and
FIG. 1B
are a top view and a cross sectional view of a conventional chemical mechanical polisher. The chemical mechanical polisher comprises a turning table
10
, a polishing pad
13
on the turning pad, a top ring
11
for retaining a wafer
12
for polish, a transportation tube
14
for slurry
19
supplying and a pump
15
for providing the slurry
19
.
While performing a chemical mechanical polishing step, the turning pad
10
and the top ring
11
are rotating along a certain direction, for example, the direction indicated by the arrow
18
a
and
18
b
. The slurry is continuously supplied onto the polishing pad
13
for polishing. Being held by the top ring
11
, the wafer
12
has a surface to be polished in contact with the polishing pad
13
, the uneven parts of the surface to be polishing is thus planarized with the aid of the slurry
19
.
The parameters to affect the effect of planarization for a chemical mechanical polishing step includes the structure and material of the polishing pad, the material of the slurry and the rotating speed of the turning table and the top ring. A structure of a conventional polishing pad is shown as FIG.
2
A. The turning table and the polishing pad are contacted with each other. The polishing pad
25
includes a lower polishing pad
24
in contact with a turning table
22
and an upper polishing pad
26
on the lower polishing pad
24
. The lower and the upper polishing pads
24
and
26
are in a circular shape with a same size that is slightly larger than the size of the turning table
22
.
FIG. 2A
to
FIG. 2C
shows an initiating step for a polishing pad to illustrate how the structure of the polishing pad affects the polishing. An unworked polishing pad
25
is shown as
FIG. 2A
, while the upper polishing pad
26
has a surface with a poor roughness that cannot perform the polishing step. Thus, as shown in
FIG. 2B
, a dresser (conditioner)
28
is used to initiate the upper polishing pad
26
to effectively achieve the polishing effect with the aid of the slurry. In addition, after the polishing pad has been used for once, the polishing pad is inevitably consumed to fail to meet the polishing requirement. The initiating step is required to perform on the polishing pad again.
The polishing pad
25
is typically designed with a larger radius than that of the turning table
22
, so that the polishing pad
25
can be renewed easily. As a consequence, the initiating effect is only resulted on the part supported by the turning table
22
. As shown in the figure, the part experienced with a direct pressure of the dresser
28
is dished, while the rim
30
of the polishing pad
25
raises relatively. A hollow part
29
is thus formed as shown in FIG.
2
C. While performing polishing on the initiated polishing pad
25
, the used slurry or polishing particle thus cannot be discharged to seriously affect the polishing effect.
To resolve the problem for discharging the used slurry or polishing particles, the projecting rim
30
is cut away, typically by notching
32
at a point from the hollow part
29
of the polishing pad
25
. While cutting the projecting rim
30
, the polisher has to be opened. Meanwhile, a great possibility of contamination is caused, and numbers of particles or defects on product are thus increased to decrease the yield of product. Moreover, the usage of the polishing pad is so frequent and the renewal rate is high. If a cutting step is required while initiating each polishing pad, the consuming time is more than half an hour. Therefore, a long time and a great effort of labor are consumed. Moreover, the operator for performing the initiating step has to be well trained. If the cutting skill is poor, problems such as unintentionally hooking the wafer retained by the top ring or wafer dropped from the top ring occur while the polishing pad is cut into too small a piece. Or the underlying material is contaminated if a notch is cut too deep.
SUMMARY OF THE INVENTION
The invention provides a composite polishing pad used in a chemical mechanical polisher. The composite polishing pad comprises an upper polishing pad and a lower polishing pad which is concentrically disposed on a turning table. The lower polishing pad has a diameter the same as that of the turning pad. Therefore, the lower polishing pad and the turning pad are overlapped with each other thoroughly. The lower polishing pad has a handler on a periphery thereof for a convenient renewal. The upper polishing pad is disposed on the lower polishing pad concentrically. The upper polishing pad has a diameter between a covering range of a dress for initiating the composite polishing pad and a covering range of a top ring for retaining a wafer to be polished.
By designing the upper polishing pad with a diameter between the dresser of the composite polishing pad and the covering range of the top ring, the formation of the projecting portion in the conventional structure is eliminated. The manually cutting or notching step is skipped. The problems the induced thereby can thus be resolved. Moreover, the design of the handler enables an operator to renew the polishing pad without opening the polisher. Thus, the contamination can be further eliminated, and the time consuming for the renewal can be shortened.
The structure of the composite polishing pad can be modified into a lamination of a lower polishing pad slight larger than the turning table and an upper polishing pad with having size between the covering ranges of the dresser and the top ring. In this manner, the composite polishing pad can be easily renewed without the formation of a handler.
Both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.
REFERENCES:
patent: 5170595 (1992-12-01), Wiland
patent: 5310455 (1994-05-01), Pasch et al.
patent: 5403228 (1995-04-01), Pasch
patent: 5605499 (1997-02-01), Sugiyama et al.
patent: 5725417 (1998-03-01), Robinson
patent: 5899745 (1999-05-01), Kim et al.
patent: 5975994 (1999-11-01), Sandhu et al.
Chou Liang-Kuei
Huang Chii-Yeh
Li Chi-Hone
Eley Timothy V.
Huang Jiawei
J.C. Patents
Nguyen Dung Van
Winbond Electronics Corp.
LandOfFree
Composite polishing pad does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Composite polishing pad, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Composite polishing pad will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2838042